What is Four?

This are selected quotes from a LinkedIn discussion in the History and Philosophy of Science Group, with added illustrations.

Tony Tramonte Chemical Engineer	Do you consider a number, for example "4" to be different depending on the class - counting, integer, real, complex, etc. or is a number a number? For example: 1, 2, 3, 4... ...-2, -1, 0, 1 2, 3, 4... 4 as a real number 4 + 0i 4 as a cardinal number 4 as an ordinal number